diff --git a/pureboot/pureboot.cpp b/pureboot/pureboot.cpp
index f365139..396c2e0 100644
--- a/pureboot/pureboot.cpp
+++ b/pureboot/pureboot.cpp
@@ -67,7 +67,7 @@ constexpr std::uint8_t timeout_seconds = PUREBOOT_TIMEOUT;
 
 // The loader's one identity number. The protocol carries none of its own —
 // a version implies it, and the host tool holds that map (README.md).
-constexpr std::uint8_t version = 3;
+constexpr std::uint8_t version = 4;
 
 // The 'b' reply, byte for byte (layout: README.md). Flash-resident because
 // no crt copies a .data image — and flash_table's storage carries the word
diff --git a/pureboot/pureboot.py b/pureboot/pureboot.py
index 5ee31bb..6a9585b 100644
--- a/pureboot/pureboot.py
+++ b/pureboot/pureboot.py
@@ -24,13 +24,13 @@ else:
     import termios
 
 PROMPT = b"+"
-VERSION = 2  # this tool's own version — free to drift from a loader's
+VERSION = 3  # this tool's own version — free to drift from a loader's
 # The loader versions this tool speaks. A pureboot version implies its wire
 # protocol, which carries no number of its own, so this window is where that
 # map lives: every version so far speaks the same protocol, and one that
 # changes it becomes the new floor here.
 OLDEST_LOADER = 1
-NEWEST_LOADER = 3
+NEWEST_LOADER = 4
 SLOT = 512  # the loader slot, on every chip
 RETRIES = 3  # rewrites of a page that reads back wrong, before the run stops